>>11256569>>11256573It's also not just that the Imperium forgets how to make things, but the vast majority of forge worlds need to make all sorts of things in nightmarishly huge quantities and at similar speed to fuel the war effort, neither of which is good for individual quality
The custodes is basically the one faction that says "No, do it RIGHT" and puts quality above both speed and quantity, in addition to the benefits of being based out of the imperial palace for facilities and knowledge
All that to say they have the knowledge, resources, facilities, and time to get the absolute best out of their gear, whereas just about no one else has all of that going for them in the galaxy
